drm/amd/display: Add callbacks for DMUB HPD IRQ notifications

[Why]
We need HPD IRQ notifications (RX, short pulse) to properly handle
DP MST for DPIA connections.

[How]
A null pointer exception currently occurs when these are received
so add a check to validate that we have a handler installed for
the notification.

Extend the HPD handler to also handle HPD IRQ (RX) since the logic is
the same.

Fixes: e27c41d5 ("drm/amd/display: Support for DMUB HPD interrupt handling")
Reviewed-by: Wayne Lin <Wayne.Lin@amd.com>
Reviewed-by: Jude Shih <shenshih@amd.com>
Acked-by: Anson Jacob <Anson.Jacob@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -217,6 +217,7 @@ static const struct drm_format_info *
 amd_get_format_info(const struct drm_mode_fb_cmd2 *cmd);
 
 static void handle_hpd_irq_helper(struct amdgpu_dm_connector *aconnector);
+static void handle_hpd_rx_irq(void *param);
 
 static bool
 is_timing_unchanged_for_freesync(struct drm_crtc_state *old_crtc_state,
@@ -683,8 +684,12 @@ void dmub_hpd_callback(struct amdgpu_device *adev, struct dmub_notification *not
 	}
 	drm_connector_list_iter_end(&iter);
 
-	if (hpd_aconnector)
+	if (hpd_aconnector) {
+		if (notify->type == DMUB_NOTIFICATION_HPD)
 			handle_hpd_irq_helper(hpd_aconnector);
+		else if (notify->type == DMUB_NOTIFICATION_HPD_IRQ)
+			handle_hpd_rx_irq(hpd_aconnector);
+	}
 }
 
 /**
@@ -760,6 +765,10 @@ static void dm_dmub_outbox1_low_irq(void *interrupt_params)
 				DRM_ERROR("DM: notify type %d invalid!", notify.type);
 				continue;
 			}
+			if (!dm->dmub_callback[notify.type]) {
+				DRM_DEBUG_DRIVER("DMUB notification skipped, no handler: type=%d\n", notify.type);
+				continue;
+			}
 			if (dm->dmub_thread_offload[notify.type] == true) {
 				dmub_hpd_wrk = kzalloc(sizeof(*dmub_hpd_wrk), GFP_ATOMIC);
 				if (!dmub_hpd_wrk) {
@@ -1560,6 +1569,10 @@ static int amdgpu_dm_init(struct amdgpu_device *adev)
 			DRM_ERROR("amdgpu: fail to register dmub hpd callback");
 			goto error;
 		}
+		if (!register_dmub_notify_callback(adev, DMUB_NOTIFICATION_HPD_IRQ, dmub_hpd_callback, true)) {
+			DRM_ERROR("amdgpu: fail to register dmub hpd callback");
+			goto error;
+		}
 #endif /* CONFIG_DRM_AMD_DC_DCN */
 	}